Full moon, more babies and busier ERs? What the data show

No, the numbers do not support it. Large studies of birth records have found no rise in births around the full moon, and hospital data show no extra emergency room visits, ambulance arrivals, trauma cases or psychiatric emergencies on full moon days. The largest birth dataset ever checked, 38.7 million births in France, found a bump of about 0.4 percent, real in the statistics but far too small for anyone on a ward to notice.

Few moon stories have been tested as thoroughly. Hospitals record everything, birth registries go back decades, and the phase of the Moon on any given day is known to the minute. This article covers what those records show, why the belief is so persistent among people who work in hospitals, and where the Moon does leave a small, measurable mark.

Why do nurses and doctors believe in the full moon effect?

What sets this story apart from most moon folklore is who tells it. It comes from midwives, emergency nurses, paramedics, doctors and police officers, people with long experience of busy nights. That gives it real weight.

The belief is common, and it has been measured. In a 1995 survey of 325 people across several occupations, 43 percent said they believed the Moon alters people’s behavior, and mental health workers held that view more strongly than other groups. Another survey, cited by psychologists Hal Arkowitz and Scott Lilienfeld, found that 45 percent of college students believe the full moon makes people prone to unusual behavior. In 2007, several police forces in the UK even added officers on full moon nights to cope with an expected rise in crime.

When people close to the action are that convinced, the question deserves a real answer. So here it is, one claim at a time.

Are more babies born during a full moon?

Births are an ideal test. Every birth is recorded with a date, and folklore makes a clear prediction: if the Moon pulls on the body the way it pulls on the oceans, labor should cluster around the full moon.

It does not. A 2005 study in the American Journal of Obstetrics and Gynecology analyzed 564,039 births from North Carolina birth certificates between 1997 and 2001, covering 62 lunar cycles. The authors found no significant differences in the number of births, the type of delivery or birth complications across the eight phases of the Moon. The same year, a study of 167,956 spontaneous vaginal deliveries in Phoenix, Arizona, from 1995 to 2000 found no link with the lunar phase either.

The pattern holds far beyond the United States:

• Austria: every child born from 1970 to 1999, 2,760,362 births over 371 lunar cycles, with no significant lunar effect.
• Germany: daily births from 1920 to 1989, drawn from national social security records, with no effect of the lunar cycle.
• India: 9,890 deliveries at a rural medical college over twelve lunar months in 2008 and 2009, with no difference between phases.
• United States, nationwide: an analysis of some 70 million birth records by astronomer Dan Caton of Appalachian State University, with no correlation.

One very large study did find something, and it is worth reading carefully. In 2021, French researchers analyzed 38.7 million births in France over 50 years and detected a very small but statistically significant rise on the day of the full moon and the day after, of about 0.4 percent. On a maternity ward with ten births a day, that works out to one extra baby every 25 full moons, roughly once every two years. The authors did not investigate the cause but suggested it could be a self-fulfilling prophecy.

What does leave a clear mark on modern birth records is the calendar on the hospital wall. Weekends and public holidays have a much more visible effect on birth numbers than the Moon has ever shown, because planned inductions and cesarean deliveries are scheduled on working days.

Are emergency rooms busier on a full moon?

The emergency room (A&E in the UK, the ED in Australia) is the other great test. In a 1996 study titled “The full moon and ED patient volumes: unearthing a myth,” two researchers reviewed all 150,999 patient visits to a suburban community hospital over four years, a period that included 49 full moons. They compared full moon days with all other days on four measures: total visits, ambulance arrivals, hospital admissions and admissions to a monitored unit. There was no significant difference on any of them.

Nearly three decades later, a 2025 study in the Journal of Orthopaedic Surgery and Research checked every one of 53,594 patients admitted to the trauma emergency department of a major regional hospital from 2018 to 2024 against the share of the Moon that was lit each day, using lunar data from the US Naval Observatory. It found no association.

The story about unsettled patients does no better. A 2026 study of 69,764 consultations at one of the largest psychiatric emergency services in France, from 2016 to 2023, found no link between the lunar phase and the number of consultations, hospital admissions, reasons for coming in or diagnoses. As far back as 1985, researchers James Rotton and I. W. Kelly pooled 37 studies on the Moon and behavior, covering crime, suicide, psychiatric problems and crisis calls, and concluded that the full moon was unrelated to any of them.

Why is the lunar effect myth so hard to shake?

If the records are that clear, why does the belief survive among people who see those records being made?

The first reason is a quirk of memory that psychologists call illusory correlation. A frantic night under a full moon is remembered, a frantic night under a half moon is not, and a quiet full moon night is not even noticed. Expectation also shapes what gets written down: one study described by Arkowitz and Lilienfeld found that psychiatric nurses who believed in lunar effects wrote more notes about patients’ odd behavior. The belief creates its own evidence.

The second reason is statistical traps. A 1982 study reported more traffic accidents on full moon nights, but in the years studied, full moons happened to fall more often on weekends, when more people drive. Once that was corrected, the effect disappeared.

The third reason lives in language. The word lunatic comes from the Late Latin lunaticus, moonstruck, and originally described a person whose madness was thought to rise and fall with the Moon. It remained in United States federal law until the 21st Century Language Act, signed on December 28, 2012, struck it out. A word that ties madness to the Moon for centuries keeps the idea alive long after anyone takes it literally.

On the maternity ward and in the ER, the full moon effect lives in memory, not in the records. The one thing the Moon measurably does is nibble at sleep.

Where the Moon does leave a mark: sleep

There is one lunar effect that holds up in several independent studies, and it is small. Around the full moon, people tend to fall asleep a little later and sleep a little less, with the biggest shift in the three to five evenings before the full moon, when the Moon is already bright after dusk. You can read the studies in detail in the full moon and sleep.

That effect may explain the myth better than any birth record. In 1999, psychiatrist Charles Raison and colleagues proposed that before electric lighting, bright moonlit nights really did cost people sleep, and that lost sleep could tip vulnerable people into episodes of illness. In their words, the full moon effect may be a cultural fossil: an observation from an age without streetlights that survived as a story after its cause faded.

And today, a nurse who has slept a little worse herself will feel an ordinary shift as heavier. The patients are not more numerous. The staff are more tired. When a tired nurse walks past a window in the small hours and sees a round Moon over the parking lot, the explanation is ready. That is not a failing, only the way human memory works, and it is why large datasets matter: they remember the quiet nights too. For the wider question of whether the Moon changes how people feel, see the full moon and mood.

Full moons in 2027: look up, but do not plan around them

If you are expecting a baby in 2027, there is no need to lay the full moon calendar next to your due date. The Moon will not bring labor forward or hold it back. The calendar does make a lovely keepsake, though: the moon phase finder shows exactly how the Moon looked on any date, including the day your child is born.

For anyone on a night shift, 2027 has twelve full moons, one each month. The brightest is the Wolf Moon of January 22, 2027, a supermoon that is exactly full at 12:17 UTC and falls on January 22 everywhere. Rising in the early evening, it will look large and golden over hospital parking lots, and the moon illusion makes it look bigger still near the horizon. Statistically, it will be a night like any other. The Cold Moon of December 13, 2027 (December 14 in Australia) rides highest in the northern sky and stays up through the longest nights of the year, while southern hemisphere readers get their long moonlit nights around the June full moon.

Every date is in the full moon calendar for 2027, and the next full moon page shows the next date and time in your own time zone. Look up on those nights. The Moon is worth it, even if it leaves the ER alone.